U.S. Pat. No. 1,823,117 is directed to achieving a more complete combustion of the fuel in the combustion chamber of a steam boiler. Rows of vertical water tubes are located at the walls of a rectangular boiler. In the central portion, four circular whirling and ascending columns of burning gases are produced by placing the wall burner fuel nozzles so that the jet from one is deflected by the jet from another at right angles thereto and repeating this arrangement at intervals around the furnace walls. However, this patent is not directed to the problem of achieving uniform heat distribution over the tubes and the tubes are not enveloped by a vortex of hot combustion gases. Such deflecting of one jet by another jet is not characteristic of the present invention in which one jet reinforces and is drawn into another jet.
U.S. Pat. No. 3,671,198 shows in FIG. 4 vertical reaction tubes and burners in the floor and roof of a furnace but the balanced, symmetrical arrangement thereof and the narrowing of the combustion chamber in the midsection precludes the development of a vortex as envisioned in the present invention. It may also be viewed as two symmetrical furnaces with a central flue gas outlet. U.S. Pat. No. 3,573,012 also shows a symmetrical arrangement in a furnace having a plurality of straight tubes extending vertically through the combustion zone wherein the burners are located on the front and back walls of the furnace in a manner to direct heat at opposite faces of each tube without establishing any vortex.
U.S. Pat. No. 3,406,804 discloses a furnace chamber having a row of vertical reactor tubes extending through the chamber and between burners located in the side walls. Rows of burners, facing towards the center, are located opposite one another, although vertically displaced. Again no attempt at creating a vortex is made.
U.S. Pat. No. 3,450,506 requires an annular configuration of a steam reformer furnace in which process tubes extend vertically, with vertical rows of burners in the walls. Burners in rows on one side are placed opposite burners on another side and are staggered so that individual burners do not directly face each other. However, they do not create a vortex that engulfs the bank of tubes.
Although furnaces having horizontal tubes are not germane to this invention, U.S. Pat. No. 2,220,387 may be noted. It discloses a furnace with horizontal process tubes and burners firing horizontally, on opposite sides of the combustion chamber, wherein a burner on one side is not positioned directly opposite a burner on the opposite side but is slightly displaced therefrom either horizontally or vertically or both. However, as FIG. 2 clearly shows, the distance or offset between the center lines of the respective opposed burners is small, e.g., 8 inches, such that streams of gases coming from opposite sides just brush one another so as to avoid direct collision, but is insufficient to promote the formation of a vortex as contemplated in the present invention. It may further be noted that this patent involves a large number of small burners and relatively short flames, whereas the present invention contemplates flames or jets of combustion gases that may be as much as 20 to 40 feet long with each burner large in firing capacity.
Other U.S. Pat. Nos. of general interest are: 2,076,871 2,079,191, 2,090,907, 2,224,827, 3,672,847.